Using plethysmographic measurements in various groups of rats, the proposed studies will determine the potency, latency to onset and duration of action of CX1942 when adminisstered either prior to, simultaneously with or subsequent to administration of either an opiate (morphine or fentanyl), a benzodiazepine (diazeman or alprazolam) in combination with an opiate or a benzodiazepine in combination with ethanol.